For incident light arrangements in microscopy, splitter elements are utilized for illumination and these splitter elements can be configured as splitter mirrors or splitter cubes. In both configurations, reflections occur at the boundary surfaces which lead to disturbances for various microscopic investigative techniques. In addition, inclined splitter mirrors diminish the quality of the image in convergent and divergent beam paths.
The splitter element is mounted in the divergent region of the imaging beam path in confocal direct-view microscopes. For this reason, both disadvantages occur when utilizing splitter mirrors. When utilizing splitter cubes, it is only necessary to do something about the reflections.
Of the in-radiated light, only a small percentage range (0.5 to 4%) returns from the object as useful light in the confocal direct-view microscopy. All reflections are superposed on the image and cause a contrast-reducing veil. Experience has shown that even reflections having an intensity of 10.sup.-4 of the maximal useful intensity can still be disturbing.
In U.S. Pat. No. 5,067,805, an effort was made to solve this problem by rotating a beam-splitter cube about a diagonal axis passing through the cube. In this way, the beams are so displaced that the arrangement no longer provides symmetry. The adjustment of such an arrangement is difficult and requires complex ancillary devices.
The use of a polarizing beamsplitter to avoid reflections, as disclosed in U.S. Pat. Nos. 4,927,254 or 4,896,952, constitutes a disturbance for anisotropic objects which are arbitrarily mounted in the microscopic beam path, that is, are not aligned to the polarized light.